The present invention relates to a paperless document information system in which a user may observe a content of a document which has been stored in an electronic image form on a CRT (cathode-ray tube) of a terminal device such as a workstation. More specifically, the present invention relates to a method for performing at a high speed, a transfer operation of document data from a data storage device to the terminal device, a display operation thereof on the terminal device, and a turning-page process operation for successively changing pages so as to be displayed thereon in a document information system having such a form that the data storage devices for electronically processing a large quantity of document data so as to be stored into a medium such as an optical disk, and also the terminal devices from which the user peruses this electronically processed document are distributively arranged and are linked by way of networks and the like.
As described in JP-A-61-255390, the conventional system is arranged by the frame memories having two pages so as to execute turning pages at a high speed. This frame memory stores not only page image data under display, but also page image data to be displayed subsequently for data utilization. With the above-described arrangement, since the turning-page operation may be realized by merely transferring the data between the frame memories, the page display change from the page under display to the subsequent page may be naturally executed.
When documents are represented as images, a total amount of image data become large. The aim of the above-described conventional system is to display image data from the frame memories at a high speed. However, no care is taken for such a point that the turning-page operation over the entire system, including the transfer operation of the document data from the storage device outside the terminal device to this terminal device, is performed at a high speed. Accordingly, more specifically in a large scale document information system where data storage devices, terminal devices and the like have been distributively arranged, there are some possibilities that a response time for a user may be prolonged since the user issues a display command until the data is actually displayed. Shortening such a response time to the display demand issued from the user may constitute an important and necessary element in order to make the system more comfortable. To achieve a large-scale document information system, both the transfer and display operations of the document data must be carried out at a high speed.
Furthermore, since the management information data used for managing the attributes or the like of the documents have been stored at the side of the data storage device in the conventional distributing document information system, the turning-page operation could not be performed at a high speed in such a manner that a selection is freely made between the turning-page operation physically designated by the user based upon the page number of the document data, and also the turning-page operation logically designated by the user based upon the content attributes of the document data, e.g., "claim" and "figure" of a patent document. As apparent from the foregoing descriptions, both of these turning-page operations must be provided to make document information systems more comfortable for any users.